With the advent of mechanical motive power in railways in the first half of the nineteenth century, the building of railroads capable of withstanding the forces produced both by the weight and speed of railway vehicles has been a fertile source of problems and engineering solutions. The basic method of building a railroad has changed little. The roadbed is smoothed and tamped and cross ties, usually relatively heavy hardwood timbers, are placed at generally uniform intervals transverse to the direction of the rails on and slightly sunken into the roadbed. A pair of tie plates each having recesses adapted to accept and limit the side-to-side motion of the base flanges of rails are placed on each tie. The rails are set in the tie plate recesses with the gauge sides opposing each other, i.e. to the inside of the track, leaving the field sides to the outside of the track. Fasteners, such as spikes, are driven into the ties through prepared holes in the tie plates so that portions of some part of the fasteners, such as portions of spike heads, overlap the rail flanges and clamp the rails and plates to the respective ties. The roadbed around and below the top surfaces of the ties is generally covered with a ballast, such as crushed stone, to anchor the ties and to prolong roadbed life.
Passing railway vehicles transmit both vertically downward and transverse forces to the rails. The transverse forces produce bending moments which tend to turn rails over with potentially disasterous consequences. Large transverse forces are transmitted to rails in roadbed curves by vehicle wheel flanges, particularly to the outside rail when the vehicles are traveling at high speed and to the inside rail on banked curves when the vehicles are moving slowly. Large rail overturning forces are also produced when a vehicle truck, on which the vehicle wheels are mounted, becomes stuck and fails to rotate to allow the wheels to follow rail curvature. In that situation, wheels "plow" into the rails producing rail overturning moments. In other circumstances, the separation of the rails may be somewhat greater than a vehicle's wheelbase causing the trucks to "hunt" or drift from side to side within the rails so that the wheels again plow into the rails.
Numerous devices have been disclosed over the relatively long history of railroading to combat the effects of the rail overturn phenomenon. Most of these devices are directed to limiting longitudinal rail creep, but all inherently have some rail overturn resistance properties. The devices typically involve a two-piece fastener generally having a C-shaped gripping knuckle or clip of some sort, a specially adapted tie plate and a spike for wedging the clip into firm contact with the rail, or, in the case of ties made of an artificial material such as concrete, a specially formed tie socket into which the clip is wedged. Without the use of a clip, a transverse force applied by a wheel flange to the upper part of the inside or gauge surface of a rail causes the rail to attempt to rotate about an axis along the field side bottom edge of the rail flange. In the overturn rotation or attempted rotation, the gauge side base flange lifts up and the edge of the flange describes an overturn path. A clip clamping, in the overturn path, the rail flange and tie plate together shifts that axis of rotation to the field side bottom edge of the tie plate, provided the clip does not break or lose its gripping power, such as from fatigue. The shifting of the axis of rotation improves rail overturn resistance because it increases the length of the lever arm which, with the vertical downward force caused by the passing vehicle, produces a counter-moment resisting overturn.
Previously disclosed clips intended for use with conventional wooden ties fall into two categories: those in which the wedged clip lies entirely above the upper surface of the tie; and those in which the clip lies in part below the upper surface of the tie. Both types of clips generally span and clamp the combined thickness of the tie plate and the rail flange. Examples of the former constructions, which avoid any notching or cutting of the ties, are found in U.S. Pat. No. 1,213,338 (Crowley), U.S. Pat. No. 1,414,784, U.S. Pat. Nos. 1,474,787, 1,551,502 (all to McVicker), U.S. Pat. No. 2,160,344 (Ryan) and U.S. Pat. No. 2,167,864 (Bailey). Each of these devices requires the use of a tie plate specially adapted on its underside to accept the clip's lower arm that is situated between the bottom of the tie plate and the upper surface of the tie. With the exception of the Bailey patent, the cited patents provide that the upper arm of the clip firmly grips the upper surface of the rail flange. The Bailey clip provides a space between the upper arm of the clip and the upper surface of the rail flange to accomodate thermal expansion. All the cited patents except those to Ryan and Bailey, provide that the stem joining the upper and lower arms of the clips bears directly on a side surface of the rail flange. Because of the constant contact of the rail flanges and clips in these constructions, the clips appear to be particularly susceptible to fatigue. Whether the overturn resistance is improved or not by these devices depends upon the effectiveness (i.e., condition) of the clip.
U.S. Pat. No. 1,531,927 (Hamilton) and German Patentschrift No. 668,649 (Rudert) disclose clips which in part extend below the upper surface of the associated wooden ties. In these constructions sockets must be specially prepared in the ties to receive the portion of the clip and related elements projecting beneath the upper surface of the tie. Specially adapted tie plates are needed to utilize both of these devices. The Hamilton clip grips the upper surface of the rail flange and the underside of the tie plate, but does not engage the underlying tie. That clip is far more difficult to use than are the other devices discussed herein, since the clip must be inserted into the rail--tie plate--tie assembly and driven into final position before the adjacent spike may be driven. The patent to Rudert, directed toward compensating for the sinking of the entire rail assembly into a softwood tie, comprises metal receptacles fitting into tie sockets and a spike protruding into each receptacle. Since in this construction the spikes (and the clips) do not engage the ties, a wedging clip gripping the underside of the tie plate within the socket and the top surface of the rail flange is provided. Reconstruction of existing railroads with either the Hamilton or Rudert constructions is particularly difficult and expensive because existing ties must have precise sockets cut in them or be removed and replaced by socketed ties.
Numerous others have proposed wedged clips for use with ties constructed of artificial materials such as asphalt and sand, concrete and metal. Examples include U.S. Pat. Nos. 858,983, 894,253, 937,054, 983,690, 1,028,674, 1,034,614, 1,242,184, and 1,390,203, wherein tie sockets adapted to accept a clip held in position by an adjacent wedge are provided. These clips have lower arms adapted to hook over a shoulder within the socket or on the bottom surface of the tie, and upper arms adapted to grip the rail base flange. All of these devices require specially adapted tie plates and ties so that these devices cannot be used in reconstruction of existing railroads unless existing ties not previously adapted to the clips are removed and replaced. None of these constructions are economically susceptible for use with wooden ties, even in new railway construction, because of the difficulty of cutting the appropriate sockets into wooden ties.